Two in one: Switchable ion conductivity and white light emission integrated in an iodoplumbate-based twin chain hybrid crystal

An iodoplumbate-based hybrid, [C₇-Apy][PbI₃] (1), where C₇-Apy⁺ = 1-heptyl-4-aminopyridinium, was prepared using a simple solution process. Three sequential phase transitions occur in the range of 402-443 K. In both the lowest and highest temperature phases, hybrid crystal 1 is composed of discrete [Pb₂I₆]_∞ twin chains surrounded by C₇-Apy⁺ cations. The connectivity between PbI₆ octahedra within a [Pb₂I₆]_∞ twin chain and the arrangement of cations are quite difference between the lowest and highest temperature phases. Hybrid crystal 1 shows switchable ion conductivity due to the structural phase transition and white light emission attributed to the broad band semiconductor emission of the twin chain. The former functionality has potential application in ion conductor devices; the single-phase white light emitter is a useful material in low-cost, easily-made, high-efficiency white light-emitting diodes.